They call it a warp drive, no doubt from science fiction. The maths is pretty hairy but the idea is interesting none-the-less. It i s based on the principle of manipulating extra dimenions from string theory. Apparantly squeezing a compact dimension inflates another. They use this as their principle.

The authors don't seem to be saying that they think we can build this now...just that it is theoretically possibe.

"We have proposed that a sufficiently advanced civilizationcould utilize this relation to generate a localizedexpansion/contraction of spacetime creating a â€˜warp bubbleâ€™in which to travel at arbitrarily high velocities. Onevital aspect of future research would be how to locallymanipulate an extra dimension. String theory suggeststhat dimensions are globally held compact by stringswrapping around them [6], [9]. If this is indeed the case,then it may be possible to even locally increase or decreasethe string tension, or even locally counter the effectsof some string winding modes. This would achievethe desired effect of changing the size of the extra dimensionswhich would lead to propulsion under this model."

I think that what excites me the most is that people are actually thinking about this. It seems to me quite possible that papers like this might in fact be laying the foundations for future interstellar missions perhaps next century!?

The most remarkable property of such concepts that in particular means the fundamental difference to other concpets in my eyes is that they really don't need speeds above the speed of light but enable interstellar travels at speeds far below that of light - because they simply make the interstellar distances much shorter.

Of course the travels require much less time than at speeds below c - but this doesn't mean that the movement occurs at speeds above c. The distance temporarily is reduced instead.

But the question is open what might happen to the vehicles themselves and their paasengers. Might they be turned smaller also? Then the problem to be solved would be unchanged.

I have no doubt that 'warp drive' FTL is possible if technically challenging, after all according to inflation theory the whole UNIVERSE traveled faster than light during Big Bang. However I do not think that induvidual FTL starships aka "Star Treck" are possible. The reason for this is the little known fact that gravitons travel at the speed of light and therefore any spacial distortions would also propogate at the speed of light. This means that warp drive would be unable to exceed the speed of light. However if one was to build a "railway" made of warp generators, it be possible to set up a space distortion wave that travels faster than light, and any object surfing this wave would also travel faster than light. The bad new is that such a "railway" would be exceedingly expencive.

There is the same "problem" with this approach, than there is with the one
from the original post: we do not know enough yet!

It is not yet clear, if "dark matter" and especially "dark energy" even exist at all. There are some quite plausible theories, that can explain the increasing rate of expansion of the universe without the need for dark energy (see "Spektrum der Wissenschaft" Issue 11/08 ).

Personally I believe it is a waste of time and resources to tinker around with ideas about what might be possible IF theory "x" proves to be right after all. If all this brainpower would be used to actually find out which theory is the "right" one, then people could start to find out all the consequences next.